Ultraviolet transmitting glass



April 1946- J. G. HOOLEY 2,398,530

ULTRA -VIOLET TRANSMITTING GLASS Filed Feb. 25, 1941 7770/ecu/ar Percen 221 l l Q 0' Q *Q E o v m 'N 9 Bnventor JOSEPH G. //00LY attorney is silica.

atented pr. 16 i946 umasvrorsr TRANSMITTING otass Joseph G. Hooley. Corning, N. Y., assignor to Corning Glass Works poration of New York 25, 1941, Serial No. 380,534

pplication r c Corning, N..Y.,' a cor- 8 Claims. (CL its-i7) phosphate glasses is meant those glasses in' which the predominating acidic constituent is phosphoric oxide as compared to silicate glasses in which the predominating acidic constituent Glasses which absorb the visible but transmit ultra-violet, such as those which contain a substantial amount of cobalt oxide, are for practical purposes designated black glasses, even though they do transmit slightly at each end of the visible spectrum and appear dense purple by transmitted light.

'ii'he primary object of this invention is to improve the ultra-violet transmission of black phosphate glasses.

Another object is to improve the stability toward devitrification of black phosphate glasses.

Another object is to increase their stability in water and acid.

A further object is to produce black phosphate glass tubing.

Still another object is to produce a black phosphate glass having a transmission of more than 50% at wave length 254 m in one millimeter thickness. r

Another object is to produce a black phosphate glass of high ultra-violettransmission which will not devitrify when drawn into tubing.

To these and other ends the invention comout exception been expressed in terms of per cent by weight and the above mentioned relationship leading to improved transmissions has heretofore been entirely ignored.

In the accompanying drawing this relationship is shown for biack phosphate glasses containing about 2% of cobalt oxide and 1% of nickel oxide (curve A), as compared with the same glasses free from cobalt and nickel (curve B). The transmissions represented by the various points of the curves were measured from pressed glass samples and were corrected to a thickness of one millimeter. Polished samples would have mission.. The glasses of curve A were made from the purest materials obtainable. Those of curve B wereslightly lesspure. Allbatches were melted reducingly by the inclusion of 1% by weight of sugar therein. The slight difierence impurity between the glasses of the two curves accounts for the fact that they cross each other as shown. and no significance is to be attached to the apparent improvement in transmission of the black glass over the clear glass at ratio 2. The true difference between the transmissions at this point for glasses of the same purity wouldamount to about 5%, the glass of curve A being less than that of curve B by about this amount. The inclecular percentage ratio PzOs/RO was increased or diminished by employing second group oxides of higher or lower molecular weights and in some prises a black phosphate glass containing cobalt oxide or cobalt and nickel oxides and at least one second group oxide, the ratio between the molecular percentages of phosphoric oxide and the total of second group oxides being between 1.3 and 2.8. Such a glass when melted reducingly from materials of suiliciently low iron content I and in a thickness of one millimeter has a transmission greater than about 50% for ultra-violet radiations of wave length 254 m I have discovered that in phosphate glasses containing cobalt and nickel there is an important relationship between their transmissions at 254 mu and their molecular percentage ratios PzOs/RO, where R0 is the total of second group diminishes with further increase in the ratio. a

The molecular percentage is determined by dividing the weight percentage of the individual oxides of-the glass by their respective molecular weights. Prior compositions have almost with instancesalso by lowering or raising the weight percentage of P205. Preferably the weight percentage of P205 should not be greater than about 75%. For obtaining the higher molecular percentage ratios of PaOs'to R0 theuse of the alkaline earth oxides is preferable." i

It will be observed that with the clear glasses of curve B the transmissions, although generally higher than those of curve A decrease linearly as the ratio is increased. 0n the other hand, the transmissions of the black glasses of curve A rise from substantially zero for a ratio of .7 to a.

maximum otabout, for a ratio of about 2.0

and thereafter diminish on further increase of above 30%. Insofar as I am aware, black phosphate glasses having a molecular percentage ratio Paoslnogreater than one have never be- 7 that the resistanceto devitriilcation increases as the ratio increases and, when the ratio exceeds about 1.4, satisfactory tubing can be produced. Therefore it will be apparent that my new glasses not only possess a higher ultra-violet transmission than prior black phosphate glasses, but the scope or their useiulness is increased by their resistance to devitrification and their higher stability to acid and water.

Theiollowing compositions in terms of percent by weight as calculated from their-respective batches will further illustrate my invention.

1 11 III IV V VI VII VIII Moi per c nt ratio Pros/- R0.

With the exception of glass III, the above compositions correspond to some of the glasses represented in curve A. They were made from pure materials and were melted reducingly by the inclusion of 1% of sugar in their batches. Glass I illustrates the low transmission which is obtained when the molecular percentage ratio PzOs/RO is 1. Glass I devitrifles too easily to make satisfactory tubing. It will be seen that the transmission rises as the ratio is increased to about 2.0 for glass V, but diminishes thereafter. As an aid to stability alumina was included in these glasses with the exception of glass 111 from which it was omitted. The presence of minor amounts of. other constituents which do not cause ultra-violet absorption is not objectionable, but too large amounts 01 such extra constituents may lower the stability. of the above examples, glasses II to VII are particularly suitable for my purposes because they have transmissions of about 50% or better and have good stability against devitrification. My researches have shown that black phosphate glasses containing cobalt oxide alone have characteristics similar to those of the above recited glasses which contain cobalt and nickel oxides. Such glasses containing cobalt oxide alone are therefore included within the scope of my invention as claimed.

What I claim is:

l. A black phosphate glass which comprises es..

' sentlally P205 and at least one second group oxide,

and which contains cobalt oxide, the molecular percentage ratio PsOs/RO being between 1.3 and 2.8, where R0 is the total of second group oxides,

the glass in a thickness of one millimeter having a transmission or at least 50% at wave length 254 my. and substantially complete absorption of visible light.

2. A- black phosphate glass which comprises eesentially P205 and at least one second group oxide, and which contains cobalt and nickel oxides, the molecular percentage ratio PzOs/RO being between 1.3 and 2.8. where R0 is the total oi secondgroup oxides, the glass in a thickness of one millimeter having a transmission of at least 50% at wave length 254 m and substantially complete absorption of visiblelight.

3. A black phosphate glass which comprises essentially'PaOs and at least one alkaline earth oxide, and which contains cobalt and nickel oxides, the molecular-percentage ratio PaOs/RO being between 1.3 and 2.8, where no is the total of second group oxides, the glass in a thickness of one millimeter having a transmission of at least 50% at wave length 254 mp and substantially complete absorption of visible light.

4. A black phosphate glass which comprises essentially P205 and at least one alkaline earth oxide, and which contains cobalt and nickel oxides, the molecular percentage ratio PcOs/RO being greater than 1.4, where R0 is the total of second group oxides, the glass in a thickness of one millimeter having a transmission of at least 50% for ultra-violet radiations oi wave length 254 m and substantially complete absorption or visible light.

5. A black phosphate glass which comprises essentially Pros and at least one second group oxide and alumina, and which contains cobalt oxide, the molecular percentage ratio PaOs/RO being between 1.3 and 2.8, where R0 is the total of second group oxides, the glass in a thickness of one millimeter having a transmission oi at least 50% at wave length 254 ma and substantially complete absorption of visible light.

6. A black phosphate glass which comprises essentiallyPzOa and at least one alkaline earth oxide and alumina, and which contains cobalt and nickel oxides, the molecular percentage ratio PzOs/RO being between 1.3 and 2.8, where R0 is the total of second group oxides, the glass in a thickness of one millimeter having a transmission of at least 50% for ultra-violet radiations of wave length 254 m and substantially complete absorption of visible light.

7. A black phosphate glass which comprises essentially P205 and at least one alkaline earth oxide, and which contains cobalt and nickel oxides, the molecular percentage ratio Pros/R0 being about 2, where R0 is the total of second group oxides, the glass ina thickness of one millimeter having a transmission of at least 50% at wave length 254 m and substantially complete absorption of visible light.

8. A glass having the approximate composition 67% P205 6% CaO, 20% BaO, 4% AlaOa, 2% C00, and 1% N10, and having in one millimeter thickness a transmission oi at least 50% at wave length 254 mu.

JOSEPH G. HOOLEY. 

